This invention relates to new and improved hydrogen ion buffers useful for biological research, and more particularly, to new aminosulfonic acid compounds having superior characteristics as buffers in such applications.
There has been a continuing need for hydrogen ion buffers between pH of six and eight since not many buffers have been known which are completely suitable in this pH range. These types of buffers are used extensively in biological research, and frequently, biologists and chemists have had to select buffers having some undesirable reactivity or toxicity, or buffers of questionable effectiveness because of the shortage of suitable and desirable buffers. For example, phosphate has been used as a buffer even though it has poor buffering capacity above pH 7.5 and tends to precipitate most polyvalent cations in many systems. Another commonly used buffer, tris-(hydroxy-methyl)aminomethane (Tris) has poor buffering capacity below pH 7.5 Moreover, it is a primary aliphatic amine of considerable reactivity and, therefore, is often inhibitory. Often the biologist has been forced to ignore the side effects of buffers in view of the unavailability of alternative buffers.
A group of hydrogen ion buffers covering the range pK.sub.a of 6.15-8.35 has been discussed by Professor Norman E. Good in Biochemistry, Volume 5, No. 2, pages 467-477, 1966. Some of these may be generally classified as substituted-amino alkylene sulfonic acid zwitterions.
There continues to be a need, however, for additional hydrogen ion buffers, and particularly buffers having increased water solubility and slightly lower pK.sub.a values which may fall within a more favorable physiological pH range. In this application, pK.sub.a is used to represent the pH of the midpoint of the buffering range of the particular composition.
Higher molecular weight organic aminosulfonic acids useful as washing and cleaning agents are described in U.S. Pat. No. 3,196,173. The acids have the general formula R.sup.1 (R.sup.2)NR.sup.3 SO.sub.3 X wherein R.sup.1 is an aliphatic, cycloaliphatic, or aliphatic-aromatic group containing at least eight carbon atoms, R.sup.2 is a hydroxy-substituted aliphatic group, R.sup.3 may be ethylene, propylene or 2-hydroxy propylene and X may be hydrogen, alkali metals or a substituted amine.